tuning.hpp: pass AFE rate and direction to tuning config, add quarter_shift field

firmware/application/tuning.hpp

@@ -33,18 +33,21 @@ struct Config {
         : first_lo_frequency(0),
           second_lo_frequency(0),
           rf_path_band(rf::path::Band::Mid),
-          mixer_invert(false) {
+          mixer_invert(false),
+          quarter_shift(0) {
     }
 
     constexpr Config(
         rf::Frequency first_lo_frequency,
         rf::Frequency second_lo_frequency,
         rf::path::Band rf_path_band,
-        bool mixer_invert)
+        bool mixer_invert,
+        uint8_t quarter_shift = 0)
         : first_lo_frequency(first_lo_frequency),
           second_lo_frequency(second_lo_frequency),
           rf_path_band(rf_path_band),
-          mixer_invert(mixer_invert) {
+          mixer_invert(mixer_invert),
+          quarter_shift(quarter_shift) {
     }
 
     bool is_valid() const {
@@ -55,9 +58,23 @@ struct Config {
     const rf::Frequency second_lo_frequency;
     const rf::path::Band rf_path_band;
     const bool mixer_invert;
+
+    /* PRALINE only: FPGA RX quarter-rate shift mode, in the encoding the
+     * gateware expects in the top two bits of register 0x03 (rx_pstep):
+     *   0b00 = none, 0b11 = up, 0b01 = down.
+     * Matches fpga_quarter_shift_mode_t in hackrf/firmware/common/fpga.h.
+     * Always 0 on HackRF One (no FPGA). */
+    const uint8_t quarter_shift;
 };
 
-Config create(const rf::Frequency target_frequency);
+/* afe_rate is the ADC sample rate in Hz (output rate << decimation), needed on
+ * PRALINE to work out how far off centre the quarter-rate shift places the
+ * analogue passband. Pass 0 (or leave defaulted) to disable the shift.
+ * transmit selects the TX tuning table. Both are ignored on HackRF One. */
+Config create(
+    const rf::Frequency target_frequency,
+    const uint32_t afe_rate = 0,
+    const bool transmit = false);
 
 } /* namespace config */
 } /* namespace tuning */